August 2023

Globally, we are seeing a surge in dengue cases. Though Malaysia did see a slight drop in cases in late July, we have recorded more deaths and more than a 100% increase in cases in comparison to the same period last year.

So, what exactly is going on?

While dengue infection can occur anytime, a warm and wet environment plays an important role in dengue transmission. In our country with higher rainfall, temperature, and humidity, that increases the possibility of transmission. The rising temperatures have become more frequent, and the extreme weather conditions can play a huge role in dengue spreading.

How can we protect ourselves then?

Aedes mosquitoes, which causes dengue, lay eggs in water-filled containers inside and surrounding the house including uncovered containers, bottles and pots that might be used to store water or may have collected rainwater. The eggs hatch when in contact with water.

So, the best preventive method is to eliminate all the mosquito egg laying sites. Items used to store water or that may collect rainwater should be properly covered or discarded to ensure no eggs are growing.

As a day-to-day protection, we can also protect ourselves by using window screens, mosquito nets, mosquito coils and repellants.

Interestingly, a few years ago, slightly more than 10 countries, including Malaysia, used Wolbachia infected-Aedes mosquitoes to reduce transmission of dengue. While there are slight differences in the Wolbachia-based control strategy in each country, all countries reported a decrease in dengue incidences at their release site.

In Malaysia, these mosquitoes were released in six sites which had persistent dengue occurrence, ranging from apartments to landed houses.

A comparison of the dengue incidence from 2013-2019 based on the Malaysian National Dengue Surveillance System showed an average of 40% decrease in all the release sites.

Wolbachia frequency also remained stable for close to a year after release cessation, suggesting long-term control of this strategy. In one of the release sites, where dengue cases were high previously despite intensive community engagement and fogging, the Wolbachia-mosquitoes successfully reduced dengue cases where fogging was no longer even considered necessary, indicating the success of this method in Selangor.

It is important to note that as there is a large movement such as to work and school, other areas would still enable import of the disease, and this may be crucial when thinking about a larger scale or longer-term implementation.

Text: Dr. Kumitaa Theva Das, Department of Biomedical Sciences, Advanced Medical and Dental Institute (IPPT), Universiti Sains Malaysia